Crystal Growth & Design最新文献

A series of previously unknown bis(acylhydrazone)s with aliphatic (zero to four CH₂ units) and aromatic (phenylene substituted) linkers was synthesized and structurally characterized. Aliphatic derivatives exhibited distinct conformational geometries and packing motifs, with linker length critically affecting hydrogen bond interactions and energies. Aromatic derivatives revealed three polymorphs of the meta-substituted structure with two of the forms related by temperature. Additionally, a bis(acylhydrazone) low-molecular-weight gelator was crystallized, revealing a unique and impressive hydrogen-bonded framework with large water channels (952 ų) and strong aliphatic and aromatic stacking interactions. These findings highlight the potential of bis(acylhydrazone)s in crystal engineering and supramolecular chemistry, especially in coformer design and selection, and supramolecular gelator applications.

Simple structural modifications of bis(acylhydrazone)s can result in dramatic solid-state effects. The aliphatic linker length critically affects hydrogen bond interactions, while aromatic linkers reveal three temperature-dependent polymorphs with a meta-phenylene linker. Additionally, a bis(acylhydrazone) supramolecular gelator structure exhibits impressive water channels and resembles a hydrogen-bonded organic framework.

NiTe₂ is a layered van der Waals transition metal dichalcogenide (TMD). We demonstrate that Ni-enriched compositional phases can be achieved in ultrathin NiTe₂ films by increasing the Ni content while maintaining the layered TMD backbone structure. The excess Ni atoms are being inserted between the NiTe₂ layers in ordered superstructures. An increase in the Ni content of thin films has been accomplished either by thermal desorption of tellurium in a vacuum at temperatures above 280°C or by postgrowth topotactical reaction of vapor-deposited Ni with the NiTe₂ film. In both cases, the same (√3 × √3) R30° superstructures are observed in low-energy electron diffraction, while X-ray photoemission spectroscopy indicates a maximum Ni concentration consistent with a Ni₅Te₆ compound. Density functional theory and scanning tunneling microscopy suggest that the excess Ni atoms are inserted in between TMD layers with octahedral coordination and forming two phases with either 1/3 or 2/3 of the octahedral sites occupied. Insertion of excess transition metals between TMD layers by topotactical reactions opens opportunities to modify NiTe₂ not just by excess Ni incorporation but also by other suitable transition metals and thus provides a potential avenue for materials engineering of layered compounds.

Here we establish bis(perfluoropyridyl)chalcogenides, ChPy^F₂ (Ch = S, Se, Te), as a new class of dual-mode donors that exploit cooperative σ- and π-hole interactions for systematic recognition of organic and organometallic planar π-systems. Supramolecular building blocks capable of predictable self-assembly offer versatile platforms for molecular assembly. The programmable nature of these dual-mode donors is demonstrated through their ability to form systematically controlled cocrystal architectures. Through strategic positioning of electron-deficient regions, these molecules achieve simultaneous engagement with π-electron-rich acceptors via both chalcogen bonding and π-stacking pathways. Systematic cocrystallization with organic aromatic hydrocarbons─from electron-rich durene to extended polycyclic systems (naphthalene, phenanthrene, pyrene, triphenylene)─produces seven distinct programmable architectures with predictably controlled coformer ratios. Normalized Ch···C distances systematically decrease from S (Nc 0.90) to Te (Nc 0.81), with interaction energies ranging from −10.9 to −20.4 kcal/mol. DFT calculations confirm that observed supramolecular architectures result from intrinsic cooperative σ/π-hole interactions rather than fortuitous crystal packing. Universal applicability is demonstrated through remarkable structural analogy between organic (phenanthrene·TePy^F₂, pyrene·TePy^F₂, triphenylene·TePy^F₂) and organometallic ([Pt(ppy)(acac)]·TePy^F₂) cocrystals, establishing design principles that transcend the organic-organometallic boundary. Energy decomposition analysis reveals that larger π-surfaces provide enhanced stabilization through augmented dispersion forces.

Two hybrid ionic salts, {[Cp₃Zr₃μ₃-O(μ₂-OH)₃]₂(C₆H₁₀O₄)₃}₂[PMo₁₂]·Cl·xSolvent (ZrAAD-PMo₁₂) and {[Cp₃Zr₃μ₃-O(μ₂-OH)₃]₂(C₆H₁₀O₄)₃}₂[SiMo₁₂]·xSolvent (ZrAAD-SiMo₁₂), were successfully synthesized via the liquid–liquid diffusion method. They were assembled from presynthesized adipic acid-directed capsular zirconium-based metal–organic cages (ZrAAD) and Keggin-type heteropolymolybdates ([PMo₁₂O₄₀]^3– and [SiMo₁₂O₄₀]^4–), respectively. Under visible light irradiation, the two hybrid salts exhibited fast and reversible photochromic behavior. Solid-state UV–vis spectra revealed new Mo⁵⁺ characteristic peaks at 740 nm (ZrAAD-PMo₁₂) and 725 nm (ZrAAD-SiMo₁₂) upon light exposure, corresponding to reduction of Mo⁶⁺. Additionally, the EPR results further confirmed the presence of Mo⁵⁺ ions after light irradiation. Furthermore, the plausible photochromic mechanism was proposed.

A molecular design strategy integrating nitrogen-rich fused-ring or 1,3,4-oxadiazole frameworks with dinitromethyl-substituted tetrazoles was developed to enhance the energetic performance. The resulting compounds combine high detonation parameters with favorable thermal stability (T_d = 127–161 °C) and mechanical insensitivity (IS = 8–30 J, FS = 120–240 N). Nitration of the 1,3,4-oxadiazole moiety in compound 10 yields outstanding performance (D_v = 8613 m·s^–1, P = 29.0 GPa, and ρ = 1.81 g·cm^–3). Single-crystal X-ray analysis shows the dinitromethyl group adopts a near-perpendicular orientation to the tetrazole, reducing π–π stacking but improving oxygen balance. In fused-ring systems, inner-salt formation disrupts conjugation and induces a twisted conformation, enhancing intramolecular electrostatic interactions and thermal stability. Importantly, introduction of a –CH₂COCH₃ substituent via chloroacetone─which is further converted to a dinitromethyl motif under nitration─facilitates successful nitramination of the oxadiazole amino group. This substituent lowers the LUMO, shifts the preferred protonation site away from the amino nitrogen, preserves the amino lone pair for attack by NO₂⁺, and, together with the nitroform fragment, improves charge delocalization and oxygen balance. Collectively, these features produce nitramino/dinitro-functionalized tetrazoles with enhanced reactivity and energetic metrics, demonstrating that coupling oxygen-rich explosophores with tunable nitrogen-rich backbones is an effective approach to high-energy, low-sensitivity energetic materials.

A simple crystalline material system (1,8-octanediammonium dihalides, ODAHX, X = Cl, Br, I) is capable of dynamically capturing molecular iodine through unique “adaptive hydrogen-bonded networks (HBNs).” The system achieves an exceptional I₂ uptake capacity up to 8.0 mol·mol^–1 (ODAHI) with >95% efficiency after 5 cycles, while time-dependent X-ray diffraction characterization identifies as many as four distinct intermediate phases for ODAHCl during iodine incorporation. Combining crystallographic analysis, adsorption kinetics, and DFT calculations, we reveal how multiple halogen-bonded motifs between halide and I₂ molecules, conformational flexibility of the organic cation, and tunable NH···X^– hydrogen bonds enable continuous structural evolution during iodine adsorption. Notably, X^–···I₂ halogen bonding initiates the adsorption and further drives the penetration of I₂ molecules, along with the synergistic adjustment of the HBNs and adaptive change of the ODAH²⁺ conformations. This work provides atomic-level evidence for spontaneous void-gas creation in originally nonporous networks and thus redefines the engineering principles for next-generation smart adsorbents targeting pollutant molecules.

Molecular crystals exhibit broad application prospects in the field of flexible functional materials due to their unique elastic behavior. This study designed and synthesized four structurally similar flexible molecular crystals with fluorescence properties. Among them, three crystals contain −C═N–NH– groups (named Bhn, Chn, Pthn), while the fourth incorporates −N═N– group (termed Modn). The mechanical response characteristics of these crystals were systematically explored through a comprehensive series of analyses. Experimental results demonstrate that, under external force stimulation, the four crystals exhibit differentiated bending performance, among which Pthn and Modn crystals can achieve complete 180° bending, showcasing excellent flexibility. Through three-point bending tests and nanoindentation techniques, the mechanical properties of these two large-sized single crystals were quantitatively characterized. It was found that they can withstand ultralarge strains of 80% and 120% respectively under extremely low stress conditions before fracturing, while also possessing low elastic moduli (E_Pthn = 3.17 ± 0.11 GPa, E_Modn = 3.75 ± 0.13 GPa) and hardness values (H_Pthn = 0.13 ± 0.02 GPa, H_Modn = 0.23 ± 0.01 GPa), confirming their outstanding mechanical flexibility and ductility. Furthermore, under ultraviolet excitation, all four crystals emit orange-red fluorescence (λ > 600 nm), but with significant differences in fluorescence intensity. This synergistic regulation effect of mechanical-optical properties provides an important theoretical foundation for developing novel intelligent flexible optoelectronic materials. Further optimization of crystal packing modes through molecular engineering strategies is expected to achieve precise control of force-light coupling characteristics, which holds significant guiding importance for promoting practical applications of such materials in fields like flexible optoelectronic sensors and adaptive optical devices.

The inductive effect of the solvent is not only a key means of regulating the material structures but also an important way to enhance the material properties. This is especially true for the crystalline porous materials formed by weak interactions such as hydrogen bonding, π conjugation, and van der Waals forces. Herein, two guanidine organophosphonate compounds were successfully obtained using 4,4′-biphenyl diphosphate acid (H₄L) and guanidine hydrochloride (G) through hydrogen-bonded interactions, with formulae [(H₄L)G]·0.5p-xyl (GP-1) and (H₄L)G (GP-2). Interestingly, the structures of the two materials exhibited completely different structural characteristics. Among them, GP-1 is a three-dimensional pillared-layer structure formed by the stacking mode of two-dimensional layers connected through hexagonal cages. On the other hand, GP-2 is a densely packed structure formed by guanidine cations connecting the upper and lower phosphonic acid layers. Meanwhile, due to the structure with a cage that well matched the shape of p-xyl, GP-1 exhibited the ability of para-xylene (p-xyl) encapsulation. The abundant continuous hydrogen-bond chains in the two structures provided the precondition to achieve proton conduction. At 80 °C and 98% relative humidity, their proton conductivity values were 5.27 × 10^–6 and 2.75 × 10^–6 S cm^–1, respectively. The rigid connection between the phosphonic acid group and the skeleton, as well as the insufficient proton source in the structure, resulted in the poor proton conductivity of both materials.

A comprehensive kinetic rate equation model is proposed for a better understanding of the Viedma deracemization of dl-amino acids. This model includes monomer plus cluster and cluster plus cluster growth, and involves both homochiral and heterochiral interactions. Our approach employs a fully microreversible growth and dissolution kinetic scheme. It works with an irreversible cluster breaking by grinding under racemizing condition of molecules. The model which is consistent with experimental observations has been parametrized on the amplification of the enantiomeric excess during the total deracemization of a scalemic mixture of dl- and l-crystals of aspartic acid. After parametrization, numerical simulations show the possibility of spontaneous mirror symmetry breaking (SMSB). Furthermore, we identify a bifurcation scenario where it is predicted that, as long as the energy difference between racemic and enantiopure crystals is not too high, Viedma deracemization may be possible under sufficient nonequilibrium conditions. However, there are situations where the deracemization success requires an initial enantiomeric excess higher than a critical value. Our model predictions have been validated by the complete deracemization of two proteinogenic amino acids, namely dl-aspartic acid and dl-valine racemic crystals.